1. Field of the Invention
The subject invention relates to methods and apparatus for guiding a web of material or tape and to web and tape guides and, for instance, has utility in magnetic tape transports, photographic film handling apparatus and other tape or web transporting or handling equipment wherein precision guidance of a tape, film or other web is required or desired.
2. Disclosure Statement
This dislcosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness, and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments subsequent in time or priority.
A large number of tape precision guiding techniques and apparatus have been proposed in the past. One repeatedly proposed tape guide has one or more tapers which urge an advancing web or tape against a reference edge or which center a web or tape, as may, for instance, be seen from U.S. Pat. No. 2,862,715, by D. N. MacDonald, issued Dec. 2, 1958, U.S. Pat. No. 2,916,228, by C. L. Wellington, issued Dec. 8, 1959, U.S. Pat. No. 3,143,270 by N. B. Cohen, issued Aug. 4, 1964, U.S. Pat. No. 3,636,825, by Randall et al, issued Jan. 25, 1972, U.S. Pat. No. 3,799,422, by R. Matsumoto, issued Mar. 26, 1974, U.S. Pat. No. 4,091,979, by L. B. Browder, issued May 30, 1978, and IBM Tedchnical Disclosure Bulletin, Vol. 10, No. 8, January 1968, p. 1096, including an article by F. R. Hertrich, entitled Guiding Mechanism for Thin Tapes, Belts or Films.
Reference may in this respect also be had to U.S. Pat. No. 1,672,846, by R. S. Dalton, issued June 5, 1928 and disclosing a tapered roller in a sheet conveyor and delivery mechanism.
In some automatic centering, guiding or rolling mechanisms, tapered rollers were made of or covered with elastic materials, as may, for instance, be seen from U.S. Pat. No. 2,592,581, by E. T. Lorig, issued Apr. 15, 1952, U.S. Pat. No. 2,660,429, by E. T. Lorig, issued Nov. 24, 1953, U.S. Pat. No. 2,729,581, by Pascoe et al, issued Jan. 3, 1956 and U.S. Pat. No. 3,196,701, by H. C. Morrow, issued July 27, 1965.
These known tapered guides lacked an agency for varying the guiding force acting on the advancing web or tape at will.
A steering roll having an elastomeric surface for supporting a web or belt is apparent from U.S. Pat. No. 3,726,588, by R. Moser, issued Apr. 10, 1973. According to that proposal, edgewise travel of the web or belt is controlled by bulging or tilting the elastomeric surface of the steering roll with applied fluid pressure.
In practice, that approach is generally limited to relatively coarse steering tasks, and is not considered suitable for high-precision web or tape guiding operations.
Existing proposals from other fields offer no remedy for such deficiencies. For instance, U.S. Pat. No. 2,702,982, by R. Guyot, issued Mar. 1, 1955, discloses filament winding and twisting apparatus employing yarn guide rollers with slanted soft flanges and using a yarn bobbin equipped with an elastic sleeve expanded by two frusto-conical flanges. After yarn has been wound on the bobbin, the flanges are removed, whereupon the sleeve contracts for separation from the wound yarn. That reference, however, fails to suggest any application of such lateral flaring principle to the guidance of any material.
U.S. Pat. No. 4,017,897, by D. L. Blanding, issued Apr. 12, 1977, discloses a tape guide which has a compound tapered configuration equipped with an angularly adjustable, washer-like ledge representing a helical edge adjacent the major diameter of the tapered guide. Inclination and vectorial direction of travel of the tape may be adjusted by angularly moving the contoured edge guide. That proposal thus merely adjusts a specially contoured tape edge guide, while providing a fixed taper. In practice, such adjustments are difficult to effect, requiring typically the use of both hands and a lot of guesswork, with imprecise results.